The present invention relates generally to a nasal mask or cannula and more particularly to a nasal cannula for treating a patient with a positive ventilation pressure machine for assisted ventilation.
Positive air pressure (PAP) assisted ventilation systems have been adopted for the treatment of various disorders. PAP systems are commonly used to treatment sleep apnea. Variations of PAP systems have been used to administer drugs and the like.
In operation the patient""s respiration is assisted by an external pump which supplies air to the patient under a slight positive pressure. In the conventional system, air is delivered in response to preset conditions selected for each individual patient. In normal operation the patient""s inspiratory phase is assisted by a pump which delivers an adequate supply of air at a slight positive pressure to a mask or cannula that is placed on the face of the patient. Full face mask systems which cover both the mouth and the nose are used. Systems which cover the mouth or nose alone are also common.
In use, when the patient exhales, the higher pressure in the mask or cannula system is used to open an exhaust valve. Thus the patient respiration is assisted on the inhalation phase by positive pressure while the expiration phase takes place at approximately atmospheric pressure.
In instances where the patient compliance is affected by the comfort of the mask it is now widely accepted that xe2x80x9cnose onlyxe2x80x9d cannula devices are preferred. Examples of current devices can be seen in U.S. Pat. No. 5,477,852 to Landis; U.S. Pat. No. 5,533,506 to Wood; U.S. Pat. No. 5,269,296 to Landis; U.S. Pat. No. 5,687,715 to Landis; U.S. Pat. No. 5,724,965 to Handke.
In contrast to prior air nasal masks, the present system includes a pair of nasal inserts which are fed bilaterally from a pair of delivery tubes which includes both a left and a right leg. If the patient occludes one leg on one side of the mask, the complimentary side is sufficient to provide all of the air required by the patient.
Air is introduced into the system through a Y-shaped adapter or coupler. The shape of the coupler cooperates with other elements to minimize noise.
A pair of bleed ports are placed in the cannula body near the patient""s nose. These bleed ports reduce the amount of carbon dioxide retained by the system. The two complex ports are placed in the cannula body to reduce noise and to reduce carbon dioxide build up in the system. Example calculations show how the size, shape and location of each of these ports cooperate to reduce the inhaled carbon dioxide concentration.
An additional feature relates directly to the shape of the nasal inserts. The nasal inserts are sufficiently long and compliant that they may be inserted into the nose until they adopt a location where the cross-section of the nare and the cross-section of the insert are essentially equal. The compliance of the material used to manufacturer the device is sufficient to provide an extremely comfortable fit in the nares.